Electromagnetic sound reproducer



March 18, 1930. G. MAEHREN 1,751,284

ELEICIlROMAGNETIC SOUND REPRODUCER Eiled March 29, 1928 INVENTOR .f2 BY Y2,

ATTORNEY '20 sequent expansion and Patented Mar. 18, 1930r UNIT-ED STATES FORNIA PATENT orner. i

GEORG-1E MAEI-IREN, OF PACIFIC GROVE, CALIFORNIA, ASSIGNOR OF ONE-THIRD TO ROCCO ELIO AND ONE-THIRD IO FRANCIS H. DAVIS, BOTH OF MONTEREY, CALI- ELECTROMAGNETIC SOUND REPRODUCER Application filed March 29, 1928. Serial No. 265,599.

My invention relates broadly lto lelectromagnetic sound reproducers and more specially to radio broadcast reception.

5 to provide amore faithful reproductionpf a broadcast than has been hitherto` obtainable, particularly 'in relation to the broadcasting of music. j j

I am a maker of fine violins, and in my present invention have adapted acoustic elements and principles that are embodied in the old masterpieces of Cremona, such as the thicknesses of the wood employed, the location, of the soundposts with relation to the bridges, and others that will appear. j Y

It should be borne in mind that loudspeakers, like violins, go to all partsl of the world and have to function under widely differing ranges of temperature, with concontraction for which adjustment means should be provided.

VMy loud-speaker is preferably a four stringed instrument, so to speak, that is capable of reproducing the whole of the musical scale by vibration of tape-like steel armatures adapted to respond to tones of different pitch and thus give full, undistorted reproduction of the tones as broadcasted. i

An object of my invention is to provide av loud-speaker instrument for radio broadcast reproduction that is extremely sensitive to radio frequencies, that is free from conflicting acoustic eddies and whose elements combine to reproduce all the tones of the musical scale.

A further object is to provide in a loudspeaker instrument a plurality of magnetic drivers adapted to actuate a plurality of companion armatures each being adapted to respond to tones of different pitch.

Another obj ectis to provide a loud-speaker instrument having a plurality of independent compensating armatures, each of which is adapted efhciently to reproduce afnitive portions of the entire range of musical frequencies when appropriately driven.

Still another object is the provision of a plurality of steel-tape armatures of varying cross-sectional areas and ybridge supportmeans therefor.y

Another object is to provide a loud-speaker instrument' wherein a resonant body carries a plurality of posts in Xed relationthereto,

being braced by interrelated spacing means, said means being adapted to carry magnetic driving units.

A further object is the provision of regulai tive adjustment means relative to said magnets and said armatures.

Another object is to .provide bracing means for the upper ends of the posts.

Another object is to providetripedal regulative means adapted to secure nice adjustment between said individualmagnet and itsy companion armature.

These objects are obtained generally by the form, material and construction 'of the parts employed, together with other objects and advantages that will hereinafter appear.

In the drawings Figure l is a plan View of myinvention.

Fig. 2 is a sectional elevational view taken on the line 1 1 of Fig. l.

Fig. 3 is a plan of, a magnet base.

Fig. lis a sectional elevational View taken on the line 11-11 of Figure 3. Y

Fig. 5 is a detached plan view ofa tripedal magnet adjuster.

Fig. 6 is a detail of anvadjustment means.

Fig. 7 shows two views of a lock-Washer.

Similar reference characters denote similar parts throughout the several views.

Referring to the drawings in detail, reference character 1 denotes the resonant body as and top 4, all of suitable seasoned wood and the posts carrying strained armatures and This invention is the outcome of the desire glued together so as to form a resonant sound-Y 'i boX; the top 4 being provided with the soundhole 5, and vertically disposed-within said box are the sound-posts 6 whose approximate location within said box is indicated by the dotted lines in Fig. l.

At regular intervals apart around the periphery of the body l and in fixed relation thereto are the vertically disposed strain posts 7, 7a, 7b, 7 C, 7d, 7 e, 7 f and 7g which eX- tend'upwardly above the top l for a suitable distance so as to carry the armature members 8, 8a, 8b and 8c at theirproper relative heights above the respective magnets 9,V 9

i and 9, said posts being linked together by the 4Q' ablylthreaded "holes 21-21--21.

braces 15.

Spaced between the posts 7 and 7a at a suitable distance above said top 4 is the horizontally disposed outer rail 10 which is preferably tenoned into a mortice as indicated in dottedlines 10e, there being similar rails 10a, 10b and 10c similarly secured to their respective posts 7b-7, l and 7e and7f--7g; whereas, said rails f1() and lOla-re suitably morticed to..receive;the tenonedends of the inner .rails 11-11 which are carried by said rails 10 and 10b with all their surfaces iiush; whilstthe inner rails 11-11 are suitably morticed to accommodate the tenonedengds of the inmost rails 12-.12g all the said rails lying in the same'h'orizontal plane.

Thejpeculiar arangement of-said rails pro-` vides what might'be `called .timbersfor carying the said magnets, in a inanneinow to be described, and as all saidmagnets are alike, andmounted alike, a description of one will sufii'ce Afor' all Albase member (Fig) is first attached f to the respectiverails 10-12 at"the`location shownin Fig. 1 by means o'f the wood-screw a which by passing through the hole 25 secures said base' to the rail 10.

` Inlthis-position the downwardly-extending lug 2lia Vengages'the inner'sid-e of the rail 12 to f whichit `is snugly and firmly secured bylthe wood-screw26athat .passes through the hole 26 andis drivendiomeinto the wood.

:It should'beimderstoodV that each magnet l, elementas 9 Iis 4provided on :the underside vided adjacent the free ends andadj acentthe apex thereof with .theholes 22-22-22that are adapted lto -accommodate the screw'adjustment means 23--23-23 which in turn have a lower threaded portion adapted to' make screw threadv engagementwith the coml plemental-means2a-24-24 of thebasemember, Fig. 3, inthe manner well'known-in detail1in2Fig.6,'or-in other suitable manner;

the same-constituting means whereby the verticalrmovcment of the screws 23 ineither up for down direction provides means for regulatively `tilting-or depressing any corner offa given-magnet as 9 so as to' bring the poles 1313 into true alinement and juxtapositional proximity with relation to thefunder partof a companion armature as 8 which extends thereover.

-Eachlend of each individual armature of the said plurality of varmatures is provided with a screwthreaded portion 16 that passes through the various v'post members 7,-78, 7b,

being supported adjacent theterminations of" the iiat part thereof by Vbridge-pieces. as 17, said bridges being of suitable height.' to carry Vsaid armature .'atthe proper distance above theYpole-pieces 18 to enable said armature to vibrante=to-4 and from said poles without making actual contact therewith.

'It should be understood that the armatures 8a and 8. are supported on higher bridgepieces 17 (than are the armaturesS and 8b; also, that'the portions of all said 'armatures which extend outwardlyfrom the said-'bridges deflect at a slightangle to the points A18 where said screwthreaded ortions pass through their respective-posts so. as'to pull down on the said respective bridges and? thus transmit vibrations from said armatureslto the top '4" and also toretain said bridges in their relative positions.

It is no'teworthy that the sound-hole 5is 'A Vof eccentric shapefresembling an ovate figure having oneflattened side,`the object of which 7 is to vary the regional tonal vibrations ofthe resonator according to therelative distances, between anyjpair ofbridges 17 andtheedge of said opening.

There is great'latitude in my reproducing instrument as :I amable torgovernlthe-so'unds emittedtherefrom'by various adjustments of .said bridges and sound posts,iby the thicknesses of said armatures and thevamount of tensve strain applied thereto. p

In order Vto operate my reproducer it @is onlynecessary to connect all the `windings of the electric elements .in series *and then attach the leads'in fthe manner usual vto yap-4v paratus of this kind whereby the driving4 energy is supplied by the audio frequency` circuit, which in turn is controlled by ther radio'energy the specific stepsvof which areV too wellknown to need detailed explanation.

It isbelievedthat the construction, Operation and advantages'o'f the Linventionuwilly now be clearly understood.v The present vembodiments o'f vthe invention have'fbeen disclosed in Vdetail 'merely' byrfway of example, since in actual practice they attain the vfea-r tures ofadvantage set'forth asbeing desir-` able in the statement of the invention 'andi-the above description.

Numerous changes in fthedetails ofA con-V struction, pand in the 'combination and -arrangement ofparts maybe resorted towith-ly out'departing fromzth'e spirit o'r scope of the invention ashereinafter claimed j orsacri'cing any of its advantages.

Having thus described my invention, what I claim as new is l. An electromagnetic sound producer comprising a hollow box-like resonant body, a plurality of co-ordinating electromagnetic drivers supported on top of said body, a companion armature for each driver, bridge means for the support of said armatures, adjustable tensing means for tensing said armatures and strain posts to hold the armatures under compensative strain above the level of the points of the strain.

2. An electromagnetic sound reproducer comprising a supporting resonant body carrying a plurality of magnetic elements adapted to drive companion armatures, strain posts carried by said body and adapted to receive the ends of said armatures and hold them under compensative strain while supported on bridge-pieces that elevate said armature above the level of said points of strain.

3. An electromagnetic sound reproducer comprising a resonant supporting body, strain-post means in vertical fixed relation to said body, outer' rail means spacing said posts and carried thereby, inner rail means carried by the outer rail means and inmost rail means carried by said inner rail means, said rails being all in the same horizontal plane and adapted to carry magnetic driving means associated with companion armatures.

4. An electromagnetic sound reproducer comprising a resonant body, two parallel armatures carried by the body and axially disposed over two companion magnets energized through the medium of an audio-frequency circuit, a duplicate set of armatures and magnets carried by' the bodyV and disposed at right angles to the Jformer, said armatures crossing eachother in dierent planes so as to form a diagrammatic square, and bridge means for the support of said armatures.

5. An electromagnetic sound reproducer comprising a resonant body, sound-posts within the body in vertical proximity to outer bridges said bridges being adapted to support armature means adapted to carry sound vibrations imported by an associated magnet energized through the medium of an audio frequency circuit. l

'6. In an electromagnetic sound reproducer having a plurality of magnetic elements energized through the medium of an audiofrequency circuit and companion armatures passing thereover, said armatures being mounted by their ends to uprights carried by the body, means for applying strain to said uprights and means coupling said uprights together in vpairs at their upper ends for mutual resistance of said strain.

7. In an electromagnetic sound reproducer having aresonant body carrying horizontallydisposed magnet elements energized through the medium of an audio-frequency circuit provided with companion armatures disposed in a fixed plane, a base means in fixed y GEORGE MAEHREN.

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